Method of making hydrocyanic acid and cyanids



Y tilled with a dilute mineral acid, onl

NITED STATES PATENT OFFICE.

MAX E. MUELLER, 0F YOUNGSTOWN, CHIC).

METHOD 0F MAKING HYDROCYANIC ACID ANI) CYAN IDS.

Application filed August 25, 1'5'19.

useful improvement in Methods of Making llydrocyanic Acid and Cyanids,of which the following is a specification, the principle of theinvention being. herein eX- plained and the best mode in which I havecontemplated applying that principle, so as to distinguish it `fromother inventions.

lt has been recognized that to obtain cyanid from ferrocyanid .in theWet Way by distilling such ferrocyanid with an acid, and absorbing theevolved hydrocyanic acid in' a caustic alkaline. solution, involvesunexpected and peculiar dilliculties. Une of these (see H. E. TWilliamsU3/mogen 00mpo'zwwis, p. 272, et seg.) is the dificulty thatr/henanallali metal ierrocyanid is disy lifty per cent. of the totalcyanogen is evolved as 'hydr-ocyanic acid, the remainder beingprecipitated, as the insoluble ferrous potassio {or'sodic7 etc.)Verrocyanid. llloreover,` in sonia methods oextracting cyanids from gasesthe cyanogen is combined in a .conipound similar to the insoluble doubleferrocyanid, from which only traces of hydro# oyanic acidare evolved bydistillation with mineral acid. For the purpose ot' overcoming thesediiiiculties, Feld Worked out a process which consisted in addingv roervcurio chlorid to the 'lerrocyanid whereby, un er proper conditions, thewhole of the c: logen content or" such iferrocyanid is converte intomercurio cyanid, from which the cyanogen may be recovered as hydrocyanicacid by distilling it with a suitable acid. Subsequently it wasdiscovered by Dewi-ance and llilliains {see British Patent No. 28,-074/08) that a small or ou'irio in conjunction with a suitable acidetlected the same result.

The present process constitutes in a sense an improvement on theaforesaid method Dewrance' and Yi/williams being based on the discoverythat in place of a kcopper salt (eitlierfcuprous or cupric), finelydivided metallic copper may be employed, with a number orp advantageousresults, as JWill be presently pointed out. A 'further object of theprocess, viz. the speeding up of the reaction, Where ac s other than hy-Specificaton of Letters Patent.

proportion of cuprous Patented July 27, 1920. Serial No. 319,702.

drochloric acid are used to bring about the conversion of ferrocyanid'sto hydrocyanic acid and cyanids, is accomplished by the addition ol asmall chlorid or other chloi'id. is the maintenance ot' theconcentrationo't the convertiii'gr acid within proper limits, suchlimits being relatively narrow.

To the accomplishment of thel foregoing and related ends, the invention,then, con- A sists of the steps hereinafter fully described andparticularly pointed out in the claims, the annexed drawingand thefollowing description setting forth in detail certain means and oneInode of carrying out the invention, such disclosed means and niodeillustrating, however, but one of various Ways in which the principle ofthe invention may be used.

ln said annexed drawings* rlie single figure there appearing'is adiagrammatic representation of an apparains designed for carrying out mypresentiinprcred process.

Where employed in conjunction, with a coke byproducts recover plant,material utilized in the present process Will ordinarily be a sludge,such as `obtained in the socalled Bueb process (see U. S. Patent No.625,964, dater. May 30, 18,99) by treating the oven gases betereremoving the ammonia therefrom with a solution of iron sulfate, orcopperas. lt Will be understood, however, that the present improvementsare not limited but may be advantageously used with forrccyanid'compounds derived from various sources. p

Referring to the aforesaid drmving, the familiar part of the apparatus,such as will be employed in the 4production ol' Eueb sludge, comprises,scrubber l in which the gas containing cyanogen compounds and ammonia istreated livitha solution oi a ierrous salt such as ferrous sulfate. Apump 2 serves 'to circulate the absorbing liquid through such scrubber,or to transfer the same in whole or part, when absorption hasv proceededsulicientl y, to u neutralizing tanlr Here the solution is neutralizedwith an acid, such as sulfuric acid, to precipitate the solubleerrocyanid, after which the mixture is elevated by of apunip flto afilter press 5 or equivalent apparatus adapted to separate out su l1precipitate. The filtrate,

amount of ammonium A further object to use with this particularmaterial,

quired into a suitable distilling vessel 10,

the latter marking the beginning of the apparatus of special interest inconnectionl with the process in hand.

This special apparatus' comprises, in association with said still 10, atank 11 containing sulfuric acid and connected to supply the latter tosaid still as desired; a combined condenser and fractioning column 12where the steam evolved with the acid from 'said still is condensed andany hydrocyanic acid absorbed by the condensed steam is again .distilledoff before the condensed steam .is discharged from the apparatus; and anabsorber 13 connected with the upper part of said condenser, a fan14`connectedwith said absorber serving to keep the latter, together withthe condenser and still, under a slight vacuum, and thus prevent escapeof hydrocyanic acid in case of any` leak developing.

he lower end o the fractioning column 12 is connected by a trappeddischarge pipe 15, so that the water condensin and collecting insaidcolumn may be ischarged. Provision is also made for injecting, steaminto the base ofA said `column as by a-valvecontrol pipe 15a in order todrive up into the upper condenser part thereof such hydrocyanic acid asis carried by such water l f discharge pipe 16, by means of as it passesdown the column. The water discharged from the latter will accordinglybe practically free of the acid.

The base of the still is connected with a which its contents, when theproper stage is reached, may be run into a` settling tank or preferablythrough suitable filters 17 as shown, whereby the insolublefcoppercyanid formed, as will presently be more fully explained, is. separatedout. The residual solution, consisting of ferrous sulfate, ammoniumsulfate, free sulfuric acid and a slight amount of copper salts, isthen` run through a tank 18 filled with scrap iron on which the copperis deposited as the metal.

The solution overflowing from tank 18 is collected in a tank 19 and thentransferred by pump 20 back to scrubber 1, to be used over again.

The general operation of the a paratus just described in exemplificationo my improved process may now be set'forth as Jneed not be described indetail.

follows, viz. The distilling vessel 10 is charged with sulfuric (orhydrochloric),

acid of the proper strength from tank 11.

In case sulfuric acid is used, a small amount of ammonium' chlorid, orother chlorid as heretofore indicated, is preferably added. A smallquantity of metallic copper is then also added to said distillingvessel, such copper being preferably in a finely divided state, andthereupon the contents of the vessel are brought to boiling. When thisstage is reached, the ferrocyanid compound is added gradually from tank8, together with a further measured quantity of acid, to bring about theliberation of the hydro cyanic acid. vIn other Words, the amount of freeacid originally charged into the distilling vessel is maintainedsubstantially constant by thus adding more acid along with theferrocyanid compound, and by regulating the amount of heat applied andthe quantity of water vapor driven off, the concentration` of such acidin the distilling vessel willv likewise remain substantially -constant.i

The manner in which the hydrocyanic acid that is freed by the reactionin the still is collected and separated, has been sufficiently indicatedin connection with the description of the apparatus. T hel solution inthe still-will of course become gradually more and more concentratedwith iron sulfate or chlorid, depending Qn which acid is used, and willhave to beremoved from such vessel after a time. As this condition isapproached, no more acid is added with the ferrocyanid compound, theaddition of the latter, however, being continued as fast as 'it isdecomposed and hydrocyanic acid given off. In this way most ofthe acidoriginally charged into the distilling vessel is utilized, so that thefinal solution in such vessel contains very little free acid. No attemptis made to distil off the hydrocyanic acid 'completely as after theferrocyanid compound has been decomposed with the formation ofcuprouscyanid the evolution of hydrocyanic acid becomes extremely slow unless afurther supply of ferrocyanid compound is added. The reaction is carriedonly so far until no ferrocyanid compounds remain undecomposed at whichtime considerable .cyanogen will still remain coins bined as cuprouscyanid. Under these conditions the insoluble material remaining in thestill which is essentially cuprous cyanid is easily separated from thesolution by settling or filtration whereas any undecomposed ferroc anidcompounds remain, the material sett es very slowly and is diiiicult tofilter. Y

Instead of recovering the copper in solution'in the tank 18 byintroducing metallic iron, it may be recovered electrolytically, as,

his metallic copper, as well as the copper cyanid from the filters 17,is returned to the still for subsequent operation of the latter. 1f theferrocyanid `material used contains impurities such as'tar or sulfurthese impurities will gradually accumulate in the copper cyanid .residuerendering the copper cyanid less ac- `not available for re-use directly.The employment of metallic copper in place of a cpper salt alsovhelps tocounteract the action ofatmospheric oxygen or erric compounds inoxidizing cuprous to cupric con pounds. The reaction is thusaccelerated, since such cuprous compounds are much more active than thecupric compounds.

Due to the manner in which the distillation is conducted by adding,along with the errocyanid compound, the proper quantity of acid forconversion of same, the concentration oi' the acid may be readilymaintained Within the proper narrow limits, c'. e. high enough so thatthe reaction will proceed at a good speed, and yet not so high as tocause partial decomposition of the hydrocyanic acid evolved. At the sametime I am able to avoid excessively diluting the alkali in which thehydrocyanic acid is absorbed. Finally it will be noted that by addingthe errocyanid compound gradually, only a small amount of such compoundremains undecomposed at' any time, thus avoiding the effect of longcontinued boiling, which renders such compound more and more diiicult todecompose into hydrocyanic acid.

Finally, the arrangement of the still, condenser and fractioning columnpermits the condensed water to flow through the fractioning column, befreed from hydrocyanic acid'and then discharged from the apparatusinstead of returning to the still. In this way, the capacity of thestill is increased and a more concentrated solutiong of ferrous sulfateand ammonium sulfate obtained.

Other modes of applying the principle of my invention may be employedinstead of the one explained, change being made as regai-ds the methodherein disclosed, provided the step or -steps stated by any of vthefollowing claims or the equivalent of such stated step or steps beemployed.

I therefore particularly -point out and distinctly claim as my inventionf 1. The method of converting errocyanids to hydrocyanic acid andcyanids, which consists in treating the ferrocyanid with metallic copperin conjunction with an acid capable of reacting with such ferrocyanidand distilling oit the hydrocyanic acid thereupon set free.

2. The method of converting ferrocyanids tohydrocyanic acid and cyanids,whichconsists in treating the ferrocyanid with iinely divided metalliccopper in conjunction. with an acid capable of reacting with suchferrocyanid and distilling oiln the hydrocyanic acid thereupon set free.

3. In a method of converting errocyanids to hydrocyanic acid andcya-nids, the steps which consist in placing metallic copper with anacid capable of reacting with such errocyanid, gradually adding theferrocyanid along with a further quantity ot such acid, and distillingoff the hydrocyanic acid thereupon set free.

i. ln a method of converting ferrocyanids to hydrocyanic acid andcyanids, the steps which consist in placing metallic copper with an acidcapable of reacting with such i'errocyanid, gradually adding theferrocyanid along with a further quantity of such acid approximatelysuiiicient to react with such ferrocyanid, whereby the amount of freeacid present is maintained substantially constant, and distilling offthe hydrocyanic acid thereupon set free.

5. In a method of converting ferrocyanids to hydrocyanic' acid andcyanids, the steps which consist in placing finely divided metalliccopper with a quantity of sulfuric acid admixed with a small amount ofammonium chlorid, gradually adding tiie iterrocyanid along with afurther quantity of such acid,

and distillingv oli' the hydrocyanic acid thereupon set free.

6. In a method of converting ferrocyanids to hydrocyanic acid andcyanidsa the steps which consist in placing finely dijvidcd metalliccopper with a quantity of sulfuric acid admixed with a small amount ofammonium chlorid, gradually adding the ferrocyanid along with a furtherquantity of such acid approximately suiicient to react with suchferrocyanid, whereby the amount of free acid present is maintainedsubstantially con. stant, and distilling oii' thehydrocyanic a'cidthereupon set free.

7. 1n a method of converting ferrocyanids to hydrocyanic acid andcyanids, the steps which consist in placing metallic copper with an acidcapable of reacting with such ferrocyanid, gradually adding theferrocyanid along with a further quantity of such acid approximatelysufficient to react with such ferrocygid, whereby the amount of reactingacid p .sent is maintained substantially constant, and distilling olfthe hydrocyanic acid set free, the addition of such further quantity ofreacting acid being discontinued when the solution becomes concentratedWith the iron salt of such acid.

8. In a method of converting ferrocyanids to hydrocyanic acid andcyanids, the Steps l which consist in placing metallic copper with anacid capable of reacting with such errocyanid, gradually adding theferrocya iid along with a further quantity of such aiid; distilling offthe hydrocyanic acid thereupon set free, and subsequently recovering thecopper from the solution.

9. In a method oficonverting ferrocyanids to hydrocyanic acid andcyanids, the steps which consist in placing metallic copper with an acidcapable of reacting With such ferrocyanid, gradually adding theferroeyanid along with a further quantity of such acid, distilling offthe hydrocyanic acid thereupon set free, separating out the insolublecopper cyanid in such solution, and then recovering the copper inmetallic form from the copper compounds remaining in such solution.

l0. In a method of converting errocyap nids to hydrocyanic acid andcyanids, the

such acid, distilling od'the hydrocyanic acid thereupon set free, andsubsequently recovn ering the copper from the solution, and

utilizing the same over again in such dis-V tilling step.

11. In a method of converting ferrocyanids to hydrocyanic acidandyanids, the

steps which consist in placing metallic cop- 1 per With a suitable acid,gradually adding the ferrocyanid along with a further quantity of suchacid, distilling oi the` hydrocyanc L.acid thereupon set free,separating out the insoluble copper cyanid in such bsolution, and thenrecovering the copperin metallic form from the copper compoundsremaining in such solution and utilizing both such copper cyanid andmetallic copper over again in such distilling step.

' Signed by me this 20th day of August, 1919. Y i

MAX E. MUELLER.

